Feature 10950 Replace pycrypto with pycryptodome

Remove the pycrypto library and change encrypt and decrypt methods to work with pycryptodome.
Move encryption methods from N2VC to common.

Change-Id: I12a5f6138664ab6ebb7100c82523e91750f05f14
Signed-off-by: Gulsum Atici <gulsum.atici@canonical.com>